The Blackheart BH5H Little Giant™ head from Blackheart Engineering™ (Crate™/Loud Technologies™) is a thoughtfully (USA) designed and well
constructed PCB amp manufactured in China. It is a very decent little 5W single-ended amp right out of the box.
The good news for the tube hobbyist community is that it has a sturdy steel chassis, a very adequate power transformer for a 5W amp (the same PT is likely used
for higher wattage models) and a nice rough black/salt n' pepper cabinet with white piping for well under $200! I think it is a big step up from the Valve Jr. and a great
platform for hand wiring and modifying with premium components.
If you already own one of these amps, I have designed a drop-in eyelet board featuring (2) Belton molded type 9-pin sockets, F&T axial filter capacitors, 2W metal film plate load resistors and a heavier
filtered DC heater supply for ultra quiet operation. I use a different tone stack with a combination MIDDLE/RAW control for more tonal variations
and more gain to work with. I also use different plate load/cathode resistors for additional gain from the single 12AX7 preamp tube. I include a progressive power switch which adds
a "standby" capability and a 12 foot right angle IEC power cord to replace the straight 5 foot stock cord. Full size 3/8" pots and set screw type black barrel knobs are
also included upgrades with an option for PEC 2W mil spec pots ($9 each or $36 for all 4). A vintage type pilot light holder with jewel is included but the hole must be made 11/16" for it to fit. The pot
holes must also be drilled out to 3/8" to accept the full size pots.
The components I feel would benefit the most from upgrading are the coupling capacitors, cathode bypass capacitors, PCB mini pots, plastic input and speaker jacks and
the plastic bobbin output transformer. I'm offering Mallory M150 coupling capacitors, Cornell Dubiliar silver mica treble capacitor, Nichicon 100V rated axial cathode bypass capacitors
and insulated Switchcraft metal jacks. I'm offering a very well made Heyboer 5K ohm paper stick-wound output transformer with paper layered and interleaved windings, grain-oriented
M-6 lamination steel and bottom lead exit for a much neater installation than the stock unit. It bolts right on and has the correct color codes for the 4, 8 and 16 ohm taps.
The complete point-to-point board kit as described and pictured above and including a layout drawing, parts list, basic installation steps, lead wire and correct metric hardware is $199 plus
shipping and includes a JJ EL84 power tube and an Electro Harmonix 12AX7 preamp tube to replace the stock Chinese tubes. No other tech support is provided so you should be an experienced tube
hobbyist to take on a project like this.
Although there are unused 5V filament leads available, I don't feel there is any benefit to adding a tube rectifier to a single ended amp because it draws the same current
whether idling or playing full volume so there is no "sag." I use these leads to power the pilot lamp. I'm working on another design which would use these 5V leads to run a
5V6GT octal power tube which would require an octal socket to be installed. This would free up a 9-pin socket for a 2 preamp tube set up. This could be used for high gain or vibrato
circuits. I have the 5V6GT tubes for anyone wanting to forge ahead with their own designs.
I'll also list separate components "a la carte" for those who want to go their own direction.
Thanks,
David Allen, EE
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